Adsorption composition and process for removal of co from material streams

ABSTRACT

Carbon monoxide is removed from streams by adsorption on an adsorption composition which comprises copper, zinc and zirconium oxides and whose copper-comprising component has a degree of reduction, expressed as weight ratio of metallic copper to the sum of metallic copper and copper oxides, calculated as CuO, of at least 45% and not more than 75%.

The present invention relates to an adsorption composition and a methodof removing CO from streams. In particular, the invention relates to anadsorption composition and a process for removing carbon monoxide fromhydrocarbon streams.

In various fields of industry, it is important to have particularly purestreams available. In this context, “pure” means that the stream is freeof constituents which would interfere in the intended use of the stream.An example is air for breathing, which has to be free of toxiccompounds. Likewise, pure streams are required in, for instance, theproduction of electronic components in order to prevent introduction ofcontaminants which adversely affect the electronic properties of thecomponents produced; among other things, particularly pure nitrogen orparticularly pure argon is often required here as protective gas.Another example is provided by catalytic chemical reactions. Catalystsare often very sensitive to poisoning. Since, for economic reasons, theamount of feed stream used per volume or mass of catalyst is usuallymaximized, even extraordinarily small amounts of impurities in the feedstream can accumulate on the catalyst and poison it. In the case ofolefin polymerization reactions of modern catalysts, for examplemetallocene catalysts, olefin streams which comprise no more than a fewppb of impurities (parts per billion, i.e. 10⁻⁹ parts of impurities perpart of the desired substance) (“polymer grade” olefins) are typicallyrequired. Olefins from typical olefin sources (steam crackers, fluidcatalytic crackers, dehydrogenations, MTO (“methanol to olefins”)processes) usually comprise very much higher proportions (ppm or evenparts per thousand range) of impurities such as carbon monoxide oroxygen (“chemical grade”); these proportions have to be reducedappropriately before use for polymerization.

The streams to be purified are typically air, nitrogen or argon orhydrocarbons such as ethylene, propylene, 1-butene, 2-butene,1,3-butadiene or styrene. Typical impurities which generally have to beremoved are oxygen and carbon monoxide and often also water, carbondioxide, hydrogen or else sulfur compounds, arsenic compounds orantimony compounds. Methods of removing such impurities from streams areknown.

Best known is the removal of carbon monoxide from oxygen-comprising gasstreams, for example air for breathing. This is usually achieved bycatalytic reaction of carbon monoxide with oxygen, generally overcopper-comprising catalysts. The most-used catalyst for this reaction ishopcalite, a copper-manganese mixed oxide which is highly active for thereaction of carbon monoxide with oxygen and over which the highly toxiccarbon monoxide reacts with oxygen to form carbon dioxide and which wasoriginally developed for removal of CO from air in breathing masks.

However, other uses of hopcalite and methods of purifying streams otherthan air for breathing are also known. Thus, WO 98/041 597 A1 disclosesa method of removing alkynes, singly or multiply unsaturatedhydrocarbons, sulfur compounds, antimony compounds or arsenic compounds,oxygen, hydrogen and carbon monoxide from streams by means of a sequenceof two or three particular catalytic and absorptive process steps. EP662 595 A1 teaches a method of removing hydrogen, carbon monoxide andoxygen from cold liquid nitrogen by bringing it into contact withparticular zeolites or other metal oxides, in particular hopcalite. EP750 933 A1 discloses a similar method of removing oxygen and carbonmonoxide from cold nitrogen or cold noble gases by bringing it/them intocontact with metal oxides, in particular hopcalite. However, at the lowtemperatures of less than −40° C. which are employed, no or very littlecatalytic reaction takes place; oxygen and carbon monoxide are adsorbedon the hopcalite and react only at higher temperature, unless they areremoved at low temperature in a desorption step. EP 820 960 A1 disclosesa method of removing oxygen and carbon monoxide from nitrogen or noblegases by bringing it/them into contact with metal oxides such ashopcalite, in particular at temperatures of from 5 50° C.

T.-J Huang and D.-H. Tsai, Catalysis Letters 87 (2003) 173-178, reportstudies on the influence of the degree of oxidation of copper on theoxidation of carbon monoxide. Cu₂O is overall more active than CuO,which is attributed to the higher mobility of oxygen in Cu₂O, comparedto Cu or CuO.

WO 02/094 435 A1 teaches a method of removing CO oxidatively fromethylene at temperatures in the range from 70 to 110° C. over catalystscomprising copper and zinc.

WO 02/026 619 A2 discloses a method of removing carbon monoxide by meansof the water gas shift reaction and WO 03/051 493 A2 discloses a methodof selectively oxidizing carbon monoxide, in particular in gas streamscomprising carbon monoxide, oxygen and hydrogen, in particular in fuelcells, and over catalysts comprising copper, a metal of the platinumgroup and a reducible metal on an oxidic support comprising activatedaluminum, zirconium dioxide, titanium dioxide, silicon dioxide, zeolitesor combinations thereof. The reducible metal oxide is selected from thegroup consisting of the oxides of Cr, V, Mo, Ce, Pr, Nd, Ti, Ni, Mn, Coand combinations thereof. U.S. Pat. No. 6,238,640 B1 describes a methodof removing carbon monoxide from hydrogen-comprising gas streams byreaction with steam and oxygen to form carbon dioxide and hydrogen inthe presence of a catalyst comprising copper oxide and aluminum oxideand also at least one metal oxide from the group consisting of zincoxide, chromium oxide and magnesium oxide.

In these methods of removing carbon monoxide in the presence of oxygen,the reaction forms carbon dioxide. In subsequent processes, this can beinert or can itself be an interfering impurity. In the latter case, itis removed, and various methods of achieving this are also known. Forexample, CA 2 045 060 A1 teaches a method of removing carbon monoxide,carbon dioxide, hydrogen, oxygen and water vapor from inert gas streamsat a temperature in the range from −30° C. to +40° C., in particularfrom −30° C. to 0° C., with carbon monoxide being reacted overtransition metal oxides such as hopcalite or copper-cobalt oxide to formcarbon dioxide and the latter being removed by adsorption on copper onan aluminum oxide support or nickel on an aluminum oxide or silicondioxide support.

However, in some applications, carbon monoxide has to be removed by amethod other than reaction with oxygen or water, for example when carbonmonoxide but no oxygen, no water or only a substoichiometric amountthereof is present in the stream to be purified. In some applications,oxygen has to be removed before the carbon monoxide, particularly whennot only carbon dioxide but also other interfering by-products can beformed. For example, oxidation products of a hydrocarbon (known as“oxygenates”) can be formed in the removal of oxygen and carbon monoxidefrom liquid hydrocarbons such as propylene, butene, butadiene or styreneover copper-comprising catalysts and are themselves interferingimpurities. In such cases, the oxygen has to be removed before removalof the carbon monoxide, and carbon monoxide cannot be removed byoxidation.

In such cases, carbon monoxide is therefore usually removed bydistillation, but removal of CO down to residual contents in the ppbrange is not possible in this way. However, adsorptive methods andadsorbents are also known for purifying streams. DE-A 1 929 977 teachescatalysts comprising from 20 to 60 parts of CuO on 100 parts of ZnO andtheir use for removing CO from ethylene and propylene streams at atemperature in the range from 50 to 200° C. U.S. Pat. No. 3,676,516teaches a supported Cu catalyst in which from 20 to 95% of the copper ispresent as Cu²⁺ and its use for removing CO from ethylene or propylenestreams at a temperature below about 200° C., in the examples actuallyabout 93° C. U.S. Pat. No. 4,917,711 discloses an adsorbent whichcomprises a copper compound on a high-surface-area support but alsoadsorbs olefins and is therefore suitable only for the purification ofnitrogen, noble gases and saturated hydrocarbons. WO 01/007 383 A1teaches a method of purifying olefin streams by passing them over porousadsorbents such as carbon black or aluminum oxide and/or silicon oxides.JP 02 144 125 A2 (CAS Abstract 113:177 506) teaches a method of removingcarbon monoxide and metal carbonyls from off gases formed insemiconductor manufacture by adsorption on adsorption compositionscomprising manganese oxide and copper oxide. JP 05 337 363 A2 (CASAbstract 120:274461) discloses adsorbents for the removal of carbonmonoxide which comprise palladium and further oxides on a support, withthe oxides being selected from among the oxides of the elements ofgroups 11, 2 and 12 (without Be, Cd, Hg and Ra), 13 (without Al, Tl andthe actinides), 14 (without C, Si, Pb and Hf), 5 and 15 (without N, P,As and the “Pa series”), 6 and 16 (without O, S, Se and U), 7 and 8 ofthe Periodic Table of the Elements.

WO 95/021 146 A1 teaches a method of removing carbon monoxide and, ifpresent, also arsine from liquid hydrocarbon streams by bringing theminto contact with a sorbent which comprises, depending on theembodiment, disperse copper in the oxidation states 0, +1 or +2 and inparticular cases also manganese dioxide. EP 537 628 A1 discloses amethod of removing carbon monoxide from alpha-olefins and saturatedhydrocarbons by bringing them into contact with a catalyst system basedon at least one oxide of a metal selected from among Cu, Fe, Ni, Co, Ptand Pd and at least one oxide of a metal selected from groups 5, 6 or 7of the Periodic Table of the Elements at from 0 to 150° C. U.S. Pat. No.4,713,090 describes an adsorbent for recovering high-purity carbonmonoxide by pressure swing adsorption or temperature swing adsorption.The adsorbent comprises a combination support having a core of siliconoxide or aluminum oxide and an outer layer of an activated carbon onwhich a copper compound is supported.

WO 2004/022 223 A2 teaches an adsorption composition comprising copper,zinc, zirconium and if desired aluminum and its use in the fully reducedstate for removing CO from streams.

Copper-comprising catalysts are also known for applications other thanthe removal of CO from inert gases or hydrocarbons. U.S. Pat. No.4,593,148 and U.S. Pat. No. 4,871,710 disclose Cu/Zn catalysts forremoval of sulfur and of arsenic. WO 95/023 644 A1 teaches a coppercatalyst for the hydrogenation of carbon oxides, for example to formmethanol, or for the shift reaction of carbon monoxide with water toform carbon dioxide and hydrogen, which catalyst comprises dispersecopper and also stabilizers such as silicon dioxide, aluminum oxide,chromium oxide, magnesium oxide and/or zinc oxide and if desired also asupport such as aluminum oxide, zirconium dioxide, magnesium oxideand/or silicon dioxide, and its activation and passivation. DE 198 48595 A1 discloses a catalyst for decomposing nitrous oxide which has thegeneral formula M_(x)Al₂O₄ in which M is Cu or a mixture of Cu and Znand/or Mg and which may comprise further dopants, in particular Zrand/or La. U.S. Pat. No. 5,328,672 teaches an automobile exhaustpurification catalyst which comprises an oxide comprising a transitionmetal and a zeolite comprising a transition metal, with the transitionmetal being selected from among Cu, Co, Ni, Cr, Fe, Mn, Ag, Zn, Ca and“compatible mixtures thereof” and preferably being identical in oxideand zeolite and particularly preferably being Cu and the oxide beingselected from among La oxide, Ti oxide, Si oxide, Zr oxide andpreferably being ZrO₂. EP 804 959 A1 discloses an NO decompositioncatalyst which in addition to copper and an MFI zeolite may furthercomprise SiO₂, Al₂O₃, SiO₂/Al₂O₃, MgO, ZrO₂ and the like and also anydesired further elements such as the transition elements Pt, Rh, Cr, Co,Y, Zr, V, Mn, Fe and Zn and also Ga, In, Sn, Pb, P, Sb, Mg and Ba,preferably P.

DE 199 50 325 A1 teaches a spinel monolith catalyst for thedecomposition of NO_(x) which has the general formulaA_(x)B_((1-x))E₂O₄, where A is Cu of which up to half can be replaced byCo, Fe, Ni, Mn or Cr, B is at least one element selected from among Zn,Mg, Ca, Zr, Ce, Sn, Ti, V, Mo and W and E is Al of which up to half canbe replaced by Fe, Cr, Ga, La or a mixture thereof. U.S. Pat. No.4,552,861 teaches a process for producing catalysts which comprise Cu,Zn, Al and at least one element from the group consisting of the rareearths and zirconium and also their use for the synthesis of methanol.The methanol catalysts disclosed in U.S. Pat. No. 4,780,481 comprise Cu,Zn and at least one alkali metal or alkaline earth metal, noble metalsand/or rare earths, with Zn being able to be partly replaced by Zr. WO96/014 280 A1 teaches catalysts which comprise Cu, Zn and at least onecompound of Al, Zr, Mg, a rare earth metal and/or mixtures thereof andtheir use for the hydrogenation of carboxylic esters. EP 434 062 A1likewise teaches a process for the hydrogenation of carboxylic estersover a catalyst comprising Cu, Al and a metal selected from the groupconsisting of Mg, Zn, Ti, Zr, Sn, Ni, Co and mixtures thereof. U.S. Pat.No. 4,835,132 describes CO shift catalysts which are produced bycalcination of a precursor of the formula(Cu+Zn)₆Al_(x)R_(y)(CO₃)_((x+y)/2)nH₂O having a layer structure, where Ris La, Ce or Zr, x is at least 1 and not more than 4, y is at least 0.01and not more than 1.5 and n is approximately 4.

Methods of activating or reactivating catalysts, includingcopper-comprising catalysts, or passivating them for transport are alsoknown. DD 0 153 761 relates to a method of activating or reactiving ironmolybdate redox catalysts which may also comprise copper, in which thecatalysts are firstly calcined in a nonoxidizing atmosphere and are thenbrought into contact with an oxidizing gas. DE 199 63 441 A1 teaches amethod of regenerating copper-comprising hydrogenation catalysts byfirstly an oxidizing treatment and then a reducing treatment, with thereduction preferably being carried out only in the hydrogenationreactor. WO 02/068 119 A1 discloses copper-comprising hydrogenation anddehydrogenation catalysts which are used in the reduced state and arepassivated for transport by partial oxidation of the copper. EP 296 734A1 describes copper-comprising shift or methanol catalysts which have aCu surface area of at least 70 m²/g, based on copper, as a result ofreduction at a temperature below 250° C. Such activation, regenerationand passivation methods are also known for other catalysts; forinstance, JP 55/003 856 A (WPI-Abstract No. WP198013664C) discloses amethod of activating catalysts based on palladium by reduction by meansof methanol, oxidation by means of oxygen, then by means of acetic acidand oxygen and final reduction by means of hydrogen. WO 03/002 252 A1describes an activation method for a cobalt-comprising catalyst bytreatment with hydrocarbon.

However, the increasing demands being made of the purity of streams forsome applications make new and improved auxiliaries and methods ofremoving impurities necessary. The removal of carbon monoxide fromhydrocarbons, in particular from hydrocarbons which are typicallypresent in liquid form, e.g. propene, 1- or 2-butene, is particularlyproblematical. It is therefore an object of the invention to find animproved adsorbent and an improved method of removing carbon monoxidefrom streams by adsorption.

We have accordingly found an adsorption composition comprising copper,zinc and zirconium oxides, wherein the copper-comprising component has adegree of reduction, expressed as weight ratio of metallic copper to thesum of metallic copper and copper oxides, calculated as CuO, of at least45% and not more than 75%. Furthermore, we have found a method ofremoving carbon monoxide from streams, in which the adsorptioncomposition of the invention is used as adsorption composition oralternatively the adsorption composition of the invention is used ascatalyst for the reaction of carbon monoxide with oxygen or as areactant with carbon monoxide. In particular, we have found a method ofremoving carbon monoxide from streams by adsorption in which the streamcomprising carbon monoxide is brought into contact with an adsorptioncomposition which comprises copper, zinc and zirconium oxides and whosecopper-comprising component has a degree of reduction, expressed asweight ratio of metallic copper to the sum of metallic copper and copperoxides, calculated as CuO, of at least 45% and not more than 75%.

The adsorption composition of the invention is well suited for use inprocesses for purifying streams, in particular for removing carbonmonoxide (CO) from liquid hydrocarbon streams such as propylene. Aparticular advantage of the adsorption composition of the invention isits ability to be regenerated readily. Although the adsorptioncomposition of the invention does not have the maximum possibleadsorption capacity for CO of such compositions, it can be regeneratedconsiderably better than compositions having a higher CO uptakecapacity. It is therefore outstandingly suitable for freeing, interalia, streams having a highly fluctuating CO content of CO in plantshaving two adsorbers of which one is being used for adsorption and oneis being regenerated.

The degree of reduction is a measure of the oxide content of the coppercomprised in the adsorption composition of the invention. The degree ofreduction is determined as the weight ratio of metallic copper, i.e.copper in the oxidation state 0 (Cu⁰) to the sum of metallic copper andcopper oxides, calculated as CuO, i.e. copper in the oxidation state+2(degree of reduction [%]=mass of Cup 100/(mass of Cu⁰+mass of CuO)).Pure metallic copper has a degree of reduction of 100%, and pure CuO hasa degree of reduction of 0%. However, a particular degree of reductiondoes not necessarily mean that the adsorption composition according tothe invention comprises metallic copper or CuO. A particular degree ofreduction can result from any possible combination of appropriateproportions of metallic copper, Cu₂O and CuO. Pure Cu₂O, i.e. copper inthe oxidation state +1, is formally an equimolar mixture of Cu and CuOand consequently has a degree of reduction of 44.4%. The degree ofreduction is determined by any method which is able to determine copperin its various oxidation states quantitatively. However, a particularlysimple method is total oxidation of the copper in a sample of theadsorption composition by bringing it into contact with air at atemperature of at least 250° C. and not more than 500° C. until theweight is constant, which should normally be after at least 10 minutesand not more than 12 hours. The degree of reduction of the sample iscalculated from the weight increase of the sample assuming that theadded weight is exclusively oxygen and assuming a stoichiometry of theoxidation of

2 Cu+O₂−>2 CuO.

The degree of reduction is generally at least 45%, preferably at least50% and particularly preferably at least 55%, and generally not morethan 75%, preferably not more than 70% and particularly preferably notmore than 65%. Examples of suitable, particularly preferred degrees ofreduction are 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63% and 64%.

In the adsorptive method of the invention, the adsorption composition ofthe invention acts by adsorption. For the purposes of the presentinvention, adsorption is the attachment of an adsorbate to the surfaceof an adsorption composition (“adsorbent”), which can generally bereversed by desorption. The adsorbate can also be reacted chemically onthe adsorbent; if the adsorbent remains essentially unchangedchemically, the process is referred to as catalysis (example: the knownmethod of reacting CO with oxygen over a metallic copper catalyst toform carbon dioxide), while if the adsorbate reacts chemically with theadsorbent, the process is referred to as absorption (examples: the knownmethod of removing oxygen from gas streams by bringing them into contactwith metallic copper to form copper(I) oxide and/or copper(II) oxide andthe known method of removing carbon monoxide from gas streams bybringing them into contact with copper(I) oxide and/or copper(I) oxideto form carbon dioxide and metallic copper). In the case of a pureadsorption as in catalysis, the adsorbate or its reaction product isremoved again from the surface by desorption, while in the case ofabsorption a chemical regeneration of the absorbent is usuallynecessary. Both in the case of catalysis and in the case of absorption,the initial step is in each case an adsorption and whether an adsorptivepurification process (e.g. in the regeneration of the adsorptioncomposition) ultimately ends in a catalytic or absorptive step or apurely adsorptive process is present depends on the individual case. Forthe purposes of the present invention, “adsorptive” means that noreduction product of carbon monoxide is released into the stream duringthe removal of CO from the stream to be purified and the adsorptioncomposition used remains essentially unchanged chemically, i.e. itscomposition does not change or changes only insignificantly. On theother hand, whether carbon monoxide or a reaction production thereof isreleased during regeneration of the adsorbent of the invention, i.e.whether or not catalysis takes place, is of no consequence for thepurposes of the invention.

Adsorption compositions or absorption compositions are in everydayspeech often also referred to as “catalysts” without actually having acatalytic action in their intended use.

The adsorption composition of the invention comprises copper, zinc andzirconium oxides. Copper can also be present partly as metallic copperand is otherwise in the form of Cu(I) and Cu(II) oxides. In pure form,the adsorption composition of the invention generally comprises copperin an amount which, calculated as CuO, corresponds to at least 30% byweight, preferably at least 50% by weight and particularly preferably atleast 60% by weight and generally not more than 99.8% by weight,preferably not more than 90% by weight and particularly preferably notmore than 80% by weight, of copper oxide CuO, in each case based on thetotal amount of the adsorption composition. The adsorption compositionof the invention in pure form generally comprises zinc oxide ZnO in anamount of at least 0.1% by weight, preferably at least 5% by weight andparticularly preferably at least 10% by weight, and generally not morethan 69.9% by weight, preferably not more than 40% by weight andparticularly preferably not more than 30% by weight, in each case basedon the total amount of the adsorption composition. In pure form, itgenerally further comprises zirconium dioxide ZrO₂ in an amount of atleast 0.1% by weight, preferably at least 3% by weight and particularlypreferably at least 5% by weight, and generally not more than 69.9% byweight, preferably not more than 30% by weight and particularlypreferably not more than 20% by weight, in each case based on the totalamount of the adsorption composition. The zirconium dioxide in theadsorption composition can be partly replaced by aluminum oxide Al₂O₃.For example, at least 1%, at least 10% or at least 30% and not more than90%, not more than 80% or not more than 70% of the zirconium dioxide inthe adsorption composition can be replaced by aluminum oxide. For thepurposes of the present invention, the expression “pure form” means thatno further constituents apart from the copper (oxide), zinc oxide andzirconium dioxide (the latter partly replaced, if desired, by aluminumoxide) components are comprised, except for insignificant constituentswhich have been, for example, carried over from manufacture, e.g.residues of starting materials and reagents, auxiliaries for shaping andthe like. “Pure form” thus means that the adsorption compositionconsists essentially of the components indicated.

The percentages of the components of the adsorption composition alwaysadd up to 100% by weight.

A very well suited adsorption composition in pure form comprises, forexample, about 70% by weight of CuO, about 20% by weight of ZnO andabout 10% by weight of ZrO₂, with the proportions adding up to 100% byweight.

The adsorption composition of the invention can but does not necessarilyhave to be present in pure form. It is possible to mix it withauxiliaries or to apply it to an inert support. Suitable inert supportsare the known catalyst supports such as aluminum oxide, silicon dioxide,zirconium dioxide, aluminosilicates, clays, zeolites, kieselguhr and thelike.

The adsorption composition of the invention is produced like knownoxidic catalysts. A convenient and preferred process for producing theadsorption composition of the invention comprises the following processsteps in the indicated order:

a) preparation of a solution of the components of the adsorptioncomposition and/or of soluble starting compounds thereof;

b) precipitation of a solid from this solution by addition of a base;

c) isolation and drying of the solid;

d) if desired calcination of the solid;

e) shaping of the solid to give shaped bodies; and

f) if desired calcination of the shaped bodies;

with the proviso that at least one of the two calcinations steps d) orf) is carried out and a step

g) setting of the degree of reduction of the copper-comprising componentof the adsorption composition, expressed as weight ratio of metalliccopper to the sum of metallic copper and copper oxides, calculated asCuO, to a value of at least 45% and not more than 75%

is carried out after or simultaneously with step f).

In the first process step, step a), a solution of the components of theadsorption composition is prepared in a customary way, for example bydissolution in an acid such as nitric acid. If desired, startingcompounds of the components of the adsorption composition, for examplethe nitrates, carbonates, hydroxycarbonates of the metals dissolved inan aqueous solution which may be acidic, for example acidified withnitric acid, are used instead of the components themselves. The ratio ofthe salts in the solution is calculated and set according to thestoichiometry of the desired final composition of the adsorptioncomposition.

A solid is precipitated as precursor of the adsorption composition fromthis solution in step b). This is carried out in a customary way, forexample by increasing the pH of the solution by addition of a base, forinstance by addition of sodium hydroxide solution or sodium carbonatesolution.

The solid precipitation product formed is generally separated off fromthe supernatant solution, for instance by filtration or decantation, andwashed with water to free it of soluble constituents such as sodiumnitrate before drying in step c). The precipitation product is thennormally dried by means of customary drying methods before furtherprocessing. In general, treatment at slightly elevated temperature, forinstance at least 80° C., preferably at least 100° C. and particularlypreferably at least 120° C., for a period of from 10 minutes to 12hours, preferably from 20 minutes to 6 hours and particularly preferablyfrom 30 minutes to 2 hours, is sufficient for this. It is also possibleand particularly convenient to convert the product of the precipitationdirectly (a certain alkali metal, for example sodium, content of theadsorption composition generally does not interfere) or after washinginto a dry further-processable powder by spray drying.

After drying, the precipitated and dried precursor of the adsorptioncomposition is, if desired, subjected to the calcination step d). Thecalcination temperature employed is generally at least 250° C.,preferably at least 300° C. and particularly preferably at least 350°C., and generally not more than 500° C.; preferably not more than 450°C. and particularly preferably not more than 410° C. The calcinationtime is generally at least 10 minutes, preferably at least 20 minutesand particularly preferably at least 30 minutes, and generally not morethan 12 hours, preferably not more 6 hours and particularly preferablynot more than 4 hours. The drying step c) and the calcination step d)can go over directly into one another.

After the drying step c) or the calcination step d), the adsorptioncomposition or its precursor is processed in the shaping step e) bymeans of customary shaping methods such as extrusion, tableting orpelletization to give shaped bodies such as extrudates, tablets orpellets, including spherical pellets.

After the shaping step, the adsorption composition or its precursor is,if desired, subjected to a calcination step f). The calcinationsconditions to be employed in step f) are identical to those of thecalcination step d).

During the course of its production, the adsorption composition issubjected to at least one of the two calcination steps d) or f), ifdesired both. In the calcination step or steps, the adsorptioncomposition precursor is converted into the actual adsorptioncomposition and, inter alia, the BET surface area and the pore volume ofthe adsorption composition are set in a customary manner with the BETsurface area and the pore volume decreasing, as is known, withincreasing calcination time and calcination temperature.

Preference is given to continuing calcination at least until thecarbonate content (calculated as CO₃ ²⁻) of the adsorption compositionis not more than 10% by weight, based on the total weight of thecalcination product, and its BET surface area is in the range from atleast 40 to not more than 100 m²/g. The pore volume of the adsorptioncomposition, measured as water absorption, is set to a value of at least0.05 ml/g during the calcination. These values are preferred for theadsorption composition of the invention.

The adsorption composition of the invention can also, as mentionedabove, be deposited on a support. This is achieved by means of customaryimpregnation processes or precipitation deposition processes. Aprecipitation deposition process is, as is known, a precipitationprocess in the presence of a support or a support precursor. To carryout a precipitation deposition process, a support or support precursoris preferably added to the solution prepared in step a) in theabove-described precipitation process. If the support is present in theform of finished preformed shaped bodies, i.e. in the case of a pureimpregnation process, the shaping step e) is omitted; otherwise, thesupport is formed during the course of processing of the precursor ofthe adsorption composition by precipitation, drying, calcination andshaping.

A preferred impregnation process for producing the adsorptioncomposition of the invention is carried out using preformed supports andcomprises the following process steps in the indicated order:

a) preparation of a solution of the components of the adsorptioncomposition and/or of soluble starting compounds thereof;

b) impregnation of a preformed support with the solution;

c) drying of the impregnated support; and

d) calcination of the impregnated and dried support,

with a step

e) setting of the degree of reduction of the copper-comprising componentof the adsorption composition, expressed as weight ratio of metalliccopper to the sum of metallic copper and copper oxides, calculated asCuO, to a value of at least 45% and not more than 75%

is carried out after or simultaneously with step d).

Process step a) of this impregnation process is carried out like theabove-described step a) of the precipitation process. In step b), apreformed support is impregnated with the solution. The preformedsupport has a shaped selected according to the application, for exampleextrudates, tablets or pellets, including spherical pellets. Theimpregnation is carried out either using supernatant solution or as animpregnation with the amount of solution corresponding to the porevolume of the support (“incipient wetness”). After the impregnation, theimpregnated support is dried and calcined like the precipitation productin the precipitation process in step c) and d). In the case of apreformed support, the shaping step is omitted.

Both in a precipitation process and in an impregnation process, a stepfor setting the degree of reduction of the copper-comprising componentis necessary. This can be effected by setting of appropriate processconditions in the calcination (in particular calcination under anatmosphere which does not oxidize copper completely) or in a separateprocess step after the calcination, with in the latter case the settingof the degree of reduction not necessarily having to be carried outdirectly after the calcination. The setting of the degree of reductionis out using any known method which is suitable for changing the degreeof oxidation of copper. If copper is predominantly present in reducedform, it is reacted with oxygen, while if copper is predominantlypresent as copper oxide, it is reacted with hydrogen.

The calcination is usually carried out in air and copper is consequentlypresent in the form of CuO in the precursor of the adsorptioncomposition of the invention obtained after the calcination. The degreeof reduction is then set by reduction of the copper to the desireddegree of reduction. This is effected by treatment of the precursorpresent after the calcination with a reducing agent. It is possible touse any known reducing agent which is able to reduce copper. The precisereduction conditions to be employed are dependent on the precursor andits composition and also on the reducing agent used and can easily bedetermined in a few routine tests. A preferred method is treatment ofthe precursor with hydrogen, usually by passing a hydrogen-comprisinggas, preferably a hydrogen/nitrogen mixture, over it at elevatedtemperature.

It is likewise possible firstly to reduce the precursor of theadsorption composition of the invention completely and subsequently tooxidize it to the desired degree of reduction. The complete reduction ofthe precursor of the adsorption composition is effected by reduction ofthe copper comprised in the adsorption composition to copper metal. Thiscan in principle be carried out using any reducing agent which is ableto reduce copper from the oxidation states I or II to the oxidationstate 0. This can be effected by means of liquid or dissolved reducingagents; in this case, drying has to be carried out after the reduction.For this reason, reduction using a gaseous reducing agent, especiallyreduction by means of hydrogen by passing a hydrogen-comprising gas overthe precursor, is very much more convenient. The temperature to beemployed here is generally at least 80° C., preferably at least 100° C.and particularly preferably at least 110° C., and generally not morethan 200° C., preferably not more than 160° C. and particularlypreferably not more than 130° C. A suitable temperature is, for example,about 120° C. The reduction is exothermic. The amount of reducing agentpassed over the precursor should be set so that the temperature does notgo outside the chosen window. The course of the activation can bemonitored with the aid of the temperature measured in the bed of theadsorbent (“temperature-programmed production, TPR”).

A preferred method of reducing the precursor of the adsorptioncomposition is to set the desired reduction temperature after a dryingstep carried out under a stream of nitrogen and to mix a small amount ofhydrogen into the stream of nitrogen. A suitable gas mixture initiallycomprises, for example, at least 0.1% by volume of hydrogen in nitrogen,preferably at least 0.5% by volume and particularly preferably at least1% by volume, and not more than 10% by volume, preferably not more than8% by volume and particularly preferably not more than 5% by volume. Asuitable value is, for example, 2% by volume. This initial concentrationis either maintained or increased in order to attain and maintain thedesired temperature window. The reduction is complete when, despite aconstant or increasing level of the reducing agent, the temperature inthe bed of the composition decreases. A typical reduction time isgenerally at least 1 hour, preferably at least 10 hours and particularlypreferably at least 15 hours, and generally not more than 100 hours,preferably not more than 50 hours and particularly preferably not morethan 30 hours.

The drying of the precursor of the adsorption composition, if necessary,is achieved by heating the precursor to a temperature of generally atleast 100° C., preferably at least 150° C. and particularly preferablyat least 180° C., and generally not more than 300° C., preferably notmore than 250° C. and particularly preferably not more than 220° C. Asuitable drying temperature is, for example, about 200° C. The precursoris maintained at the drying temperature until only residues of adheringmoisture which no longer interfere are present; this is generally thecase after a drying time of at least 10 minutes, preferably at least 30minutes and particularly preferably at least 1 hour, and generally notmore than 100 hours, preferably not more than 10 hours and particularlypreferably not more than 4 hours. Drying preferably takes place in a gasstream in order to transport the moisture out of the bed. It ispossible, for example, to use dry air for this purpose, but particularpreference is given to passing an inert gas, in particular nitrogen orargon, through the bed.

After complete reduction, the degree of reduction is set to the desiredvalue by oxidation of the adsorption composition precursor. This can beeffected by means of any known oxidizing agent which can oxidize copper.Oxygen, in particular air or an oxygen/nitrogen or air/nitrogen mixture(“lean air”), is conveniently used for this purpose. A preferred methodof oxidizing the precursor of the adsorption composition is to stop thesupply of hydrogen after the reduction, to flush the residual hydrogenpresent out of the reaction vessel by means of nitrogen, then to set thedesired oxidation temperature and to mix a small amount of oxygen intothe stream of nitrogen. Temperature, total amount of gas, oxygen contentand treatment time have to be optimized in each individual case byroutine experiments with determination of the degree of reduction. Atypical suitable gas mixture comprises, for example, at least 0.05% byvolume of oxygen in nitrogen, preferably at least 0.1% by volume andparticularly preferably at least 0.15% by volume, and not more than 0.5%by volume, preferably not more than 0.4% by volume and particularlypreferably not more than 0.25% by volume. A suitable value is, forexample, 0.2% by volume. A typical oxidation time is generally at least24 hours, preferably at least 48 hours and particularly preferably atleast 60 hours, and generally not more than 100 hours, preferably notmore than 90 hours and particularly preferably not more than 80 hours.For example, oxidation is carried out for 70 hours. The amount of gas tobe employed is typically at least 2000 standard l of gas per liter ofadsorption composition precursor and hour (standard l=standard liters,i.e. at 0° C. and atmospheric pressure), preferably at least 2500standard l/l*h and particularly preferably at least 2800 standard l/l*h,and generally not more than 4000 standard l/l*h, preferably not morethan 3500 standard l/l*h and particularly preferably not more than 3200standard l/lh. For example, 3000 standard l/l*h are well suited. Thetemperature set is generally at least 30° C., preferably at least 35° C.and particularly preferably at least 40° C., and generally not more than80° C., preferably not more than 70° C. and particularly preferably notmore than 60° C. For example, 50° C. are well suited.

To use the shaped adsorption composition bodies, they are introducedinto a vessel usually referred to as an “adsorber” but sometimes also“reactor” in which they are brought into contact with the stream to bepurified.

Before the finished adsorption composition is used for adsorption of CO,it is preferably dried (if appropriate once again) in order to removetraces of adhering moisture and to increase the adsorption capacity. Thedrying of the finished adsorption composition is carried out like theabove-described drying of its precursor.

The setting of the degree of reduction and the drying are convenientlycarried out in the adsorber since otherwise great efforts have to bemade to protect the ready-to-use activated adsorption composition fromair and moisture while introducing it into the adsorber.

After the setting of the degree of reduction and any drying carried outbefore or after the setting of the degree of reduction, the adsorptioncomposition of the invention is ready for operation.

The adsorptive method of the invention is a method of removing carbonmonoxide from streams by adsorption, in which the stream comprisingcarbon monoxide is brought into contact with an adsorption compositionwhich comprises copper, zinc and zirconium oxides and whosecopper-comprising component has a degree of reduction, expressed asweight ratio of metallic copper to the sum of metallic copper and copperoxides, calculated as CuO, of at least 45% and not more than 75%. Theadsorptive method of the invention is thus distinguished by the use ofthe adsorption composition of the invention. An advantage of theadsorptive method of the invention is its applicability to streams whichare either free of oxygen and are at a temperature which is insufficientfor the conventional catalytic reaction of carbon monoxide with oxygento form carbon dioxide or in whose further use carbon dioxide oroxygenates interfere.

In principle, any stream, for example inert gas streams (nitrogen,helium, neon, krypton, xenon and/or argon) or hydrocarbon streams suchas alkanes (methane, ethane, propane, butane, mixtures thereof, isomersand isomer mixtures) or alkenes (also known as “olefins”) such asethene, propene, 1-butene, 2-butene, 1,3-butadiene and/or styrene, canbe freed of contamination by carbon monoxide by means of the adsorptivemethod of the invention.

It is likewise possible to use the adsorption composition of theinvention in a nonadsorptive manner to remove carbon monoxide. This isparticularly advantageous when the stream to be freed of carbon monoxidecomprises not only carbon monoxide but also oxygen and is at atemperature which is sufficiently high for the catalytic reaction ofoxygen with carbon monoxide and in whose further use carbon dioxide oroxygenates do not interfere. Thus, carbon monoxide in streams comprisingcarbon monoxide and oxygen can be reacted by catalytic reaction withoxygen over the adsorption composition of the invention used as catalystto form carbon dioxide and thus be removed from the stream. Likewise,carbon monoxide can be removed from streams comprising carbon monoxideby reaction of carbon monoxide with an adsorption composition accordingto the invention comprising copper(I) oxide and/or copper(II) oxide toform metallic copper and carbon dioxide. It is equally possible toremoved oxygen from streams by adsorption on the adsorption compositionof the invention comprising metallic copper with formation of copper(I)oxide and/or copper(II) oxide, or in the presence of hydrogen bycopper-catalyzed formation of water. As in the case of othercopper-comprising compositions, not only carbon monoxide, oxygen andtogether with the latter also hydrogen, but also other contaminantswhich react with copper or copper oxide, for example elemental mercuryand/or mercury-, sulfur-, antimony- and/or arsenic-comprising compounds,can be removed from streams by means of the adsorption composition ofthe invention. In other words: the adsorption composition of theinvention can be used in all known processes in which copper-comprisingsolids are used catalytically, absorptively or as reactants.

The adsorptive method of the invention is preferably used for removingcarbon monoxide from alkene streams, in particular for removing carbonmonoxide from alkene streams which are usually in liquid form. Alkenesin liquid form typically do not have, except when unusually highpressures are employed, the temperature necessary for the catalyticremoval of carbon monoxide by reaction with oxygen, and in addition theoxygenate formation would interfere in the subsequent use forpolymerization.

The adsorptive method of the invention is particularly useful forremoving carbon monoxide from propene, 1-butene, 2-butene,1,3-butadiene, butene mixtures, butene/butadiene mixtures or styrene inorder to reduce the carbon monoxide content to the values permissiblefor “polymer grade” olefins. In a very particularly preferredembodiment, carbon monoxide is removed adsorptively from liquid propeneby means of the method of the invention.

The adsorptive method of the invention makes it possible to removecarbon monoxide from streams. It is particularly useful for removingcarbon monoxide from streams which generally comprise at least 0.001 ppm(ppm by volume in the case of gases, ppm by weight in the case ofliquids), preferably at least 0.01 ppm, and generally not more than 1000ppm, preferably not more than 100 ppm and particularly preferably notmore than 10 ppm, of carbon monoxide. In the case of relatively highinitial concentrations of carbon monoxide, it is usually more economicalto carry out another known purification methods such as distillation,catalytic oxidation of the carbon monoxide by means of oxygen to formcarbon dioxide or oxidation of the carbon monoxide by means of copperoxide to form metallic copper and carbon dioxide, if desired withsubsequent removal of carbon dioxide and oxygenates, beforehand sinceotherwise the adsorption capacity of the adsorption composition can bereached too quickly.

To carry out the adsorptive method of the invention, the stream to befreed of carbon monoxide is passed over the bed of the shaped bodies ofthe adsorption composition of the invention in the adsorber.

The temperature for the adsorptive method of the invention is notcritical or relatively noncritical from a technical point of view.Typical temperatures are in the range of at least −270° C., preferablyat least −100° C. and particularly preferably −40° C., and not more than300° C., preferably not more than 200° C. and particularly preferablynot more than 100° C. The temperature is conveniently not influencedseparately but the method of the invention is instead carried out at thetemperature of the stream to be treated.

The important parameter which determines the degree of depletion is,apart from the temperature which is, as described, conveniently notinfluenced separately, the contact time between stream and adsorptioncomposition. This contact time is determined by the flow rate of thestream and the volume of the bed of adsorption composition. The volumeflow of the stream to be purified will usually be determined by thecapacity of parts located upstream or downstream. Furthermore, theadsorption capacity of the adsorption composition is limited, so that aparticular amount of adsorption composition can be utilized for themethod of the invention for a particular time before it has to beregenerated. Although this makes the use of a very large amount ofadsorption composition desirable, the costs which increase with the sizeof the adsorber stand in the way of this. The amount of adsorptioncomposition in the adsorber is therefore selected in the individual caseso that firstly the desired degree of depletion and secondly a tolerablyshort operating time of an adsorber between two regenerations of theadsorption composition are achieved. It is advantageous to provide atleast two adsorbers of which at least one can be supplied with thestream to be purified while the adsorption composition in at least oneother is regenerated. This is a routine optimization exercise for aperson skilled in the art.

Depending on the adsorber size selected, the maximum uptake capacity ofthe adsorption composition present therein for carbon monoxide so thatit has to be regenerated is reached sooner or later.

To regenerate the adsorption composition of the invention, the stream tobe purified is firstly stopped; it is preferably fed into a paralleladsorber filled with fresh or regenerated adsorption composition.

The adsorption composition to be regenerated is subsequentlyregenerated. This occurs by desorption. Here, it is immaterial whetherthe adsorbed carbon monoxide reacts catalytically with any adsorbedoxygen or purely chemically by reaction with copper oxide present in theadsorption composition to form carbon dioxide or in another way, forinstance with any hydrogen present to form methanol or methane, prior tothe desorption and these reaction products are subsequently desorbed;the important thing is the reestablishment of the adsorption capacity ofthe adsorption composition.

Desorption is carried out by passing a fluid, preferably a gas, over theadsorption composition, by increasing the temperature or by means of acombination of these measures. A preferred procedure is to pass a gasthrough the adsorber in which the adsorption composition to beregenerated is present and at the same time heating the adsorber. Thegas can be inert, for example nitrogen, methane or argon, but it is alsopossible to use hydrogen in which case the CO is converted into methanolor methane. The desorption temperature is generally set to a value of atleast 50° C., preferably at least 100° C. and particularly preferably atleast 150° C., and generally not more than 500° C., preferably not morethan 450° C. and particularly preferably not more than 400° C. Forexample, a desorption temperature of about 300° C. is suitable. Theduration of the regeneration is typically at least 1 hour, preferably atleast 10 hours and particularly preferably at least 15 hours, andgenerally not more than 100 hours, preferably not more than 50 hours andparticularly preferably not more than 30 hours.

To replace oxygen lost from the copper, it is often advantageous tocarry out the desorption using an inert gas, preferably nitrogen orargon, comprising traces of oxygen. It is convenient to use nitrogenwhich generally comprises oxygen in an amount of at least 1 ppm,preferably at least 5 ppm and particularly preferably at least 10 ppm,and generally not more than 300 ppm, preferably not more than 250 ppmand particularly preferably not more than 200 ppm, for desorption.

The actual desorption can also be initiated with the removal of residualstream to be purified from the adsorber by flushing of the adsorber,advantageously at room temperature with the gas stream used fordesorption.

After this regeneration, the absorption composition is generally readyfor immediate renewed use. In particular cases, especially when thedesired degree of reduction has changed too much, it can be advisable ornecessary to subject the adsorption composition to renewed setting ofthe degree of reduction.

The adsorption composition of the invention, and the adsorptive methodof the invention make it possible to remove carbon monoxide from streamsin a simple and economical way. The streams which have been purified inthis way can subsequently be employed for their intended use.

1-5. (canceled)
 6. A method of removing carbon monoxide from streamscomprising carbon monoxide by adsorption on an adsorption composition,wherein the stream comprising carbon monoxide is brought into contactwith an adsorption composition comprising copper, zinc and zirconiumoxides, wherein the copper-comprising component has a degree ofreduction, expressed as weight ratio of metallic copper to the sum ofmetallic copper and copper oxides, calculated as CuO, of at least 45%and not more than 75%.
 7. The method according to claim 6, whereincarbon monoxide is removed from a liquid propylene stream.
 8. A methodof removing carbon monoxide from streams comprising carbon monoxide andoxygen by catalytic reaction of carbon monoxide with oxygen to formcarbon dioxide, wherein the adsorption composition defined in claim 6 isused as catalyst.
 9. A method of removing carbon monoxide from streamscomprising carbon monoxide by reaction of carbon monoxide with a solidcomprising copper(I) oxide and/or copper(II) oxide to form carbondioxide and metallic copper, wherein the adsorption composition definedin claim 6 is used as solid comprising copper(I) oxide and/or copper(II)oxide.
 10. A process for producing the adsorption composition defined inclaim 6, which comprises the following process steps in the indicatedorder: a) preparation of a solution of the components of the adsorptioncomposition and/or of soluble starting compounds thereof; b)precipitation of a solid from this solution by addition of a base; c)isolation and drying of the solid; d) if desired calcination of thesolid; e) shaping of the solid to give shaped bodies; and f) if desiredcalcination of the shaped bodies; with the proviso that at least one ofthe two calcination steps d) or f) is carried out, wherein the processcomprises a process step g) setting of the degree of reduction of thecopper-comprising component of the adsorption composition, expressed asweight ratio of metallic copper to the sum of metallic copper and copperoxides, calculated as CuO, to a value of at least 45% and not more than75% to be carried out after or simultaneously with process step f). 11.A process for producing the adsorption composition defined in claim 6,wherein zinc is present in the form of zinc oxide and zirconium ispresent in the form of zirconium dioxide, and which comprises thefollowing process steps in the indicated order: a) preparation of asolution of the components of the adsorption composition and/or ofsoluble starting compounds thereof; b) impregnation of a preformed inertsupport with the solution; c) drying of the impregnated support; and d)calcination of the impregnated and dried support, wherein the processcomprises a process step e) setting of the degree of reduction of thecopper-comprising component of the adsorption composition, expressed asweight ratio of metallic copper to the sum of metallic copper and copperoxides, calculated as CuO, to a value of at least 45% and not more than75% to be carried out after or simultaneously with process step d). 12.A method of regenerating the adsorption composition defined in claim 6after it has been used for the adsorptive removal of carbon monoxidefrom streams comprising carbon monoxide, wherein the adsorptioncomposition is heated to a temperature in the range from 50 to 500° C.and/or a gas is passed through a bed of the adsorption composition to beregenerated.